Method for making integrated circuit aluminium panels

ABSTRACT

The invention relates to an aluminium OSF integrated circuit panel production method comprising surface preparation of two aluminium alloy sheets, deposition on one of the sheets of a weld-proof ink in reserved areas corresponding to the design of the circuit, connection by rolling of the sheets together, and expansion of the channels corresponding to the non-welded areas using a pressurised fluid, wherein one of the sheets is made of 1000 series alloy and the other of an alloy containing iron and manganese and such that Fe+Mn&gt;0.8% (by weight), and preferentially &gt;1, or 1.5%. The iron and manganese alloy is preferentially obtained by continuous casting of strips between two cooled rolls. 
     The invention also relates to a continuous aluminium alloy integrated circuit panel production method.

This application is a filing under 35 USC 371 of PCT/FR2001/03886 filedDec. 7, 2001.

FIELD OF THE INVENTION

The invention relates to a method to produce integrated circuitaluminium panels, generally known as roll-bond, two-sided with twodeformed sides or OSF (one side flat) with one flat side and onedeformed side. These panels are produced from two aluminium or aluminiumalloy sheets, one of which is coated, on the areas intended for theintegrated circuit, with an ink intended to prevent welding between thetwo sheets. The two sheets are then welded by co-rolling. The non-weldedareas are then expanded using hydraulic or pneumatic means to form acircuit, wherein the essential part is used as a heat exchanger,particularly as a refrigeration circuit in household refrigerators.

DESCRIPTION OF RELATED ART

The book “L'aluminium”, volume 1“Production—Propriétés—Alliages—Fabrication desdemi-produits—Fabrications annexes”, published by Editions Eyrolles,Paris 1964, pages 718–721, and the publication “Panneaux aluminium àcircuits intégrés: deux lignes de fabrication complémentaires pour demultiples produits”, published in La Revue de l'Aluminium, February1982, described the principle of the roll-bond method to producetwo-sided type panels and disclosed the diagram of a continuousproduction line, and the alloys generally used for panel manufacture. Insaid continuous production line, the panels are formed from individualsheets (referred to as “plates” in the book), which are conveyedmanually or using mechanical conveyance means through the differentmachines forming the production line.

The patent FR 1347949 (Olin Mathieson) describes the principle of OSFintegrated circuit panels and proposes to produce them from two sheetsof different mechanical resistance, one made of 1100 alloy and the otherof 1100 alloy with 0.12% added zirconium.

The patent FR 2561368 (Cegedur Pechiney) discloses a continuousproduction method for OSF type roll-bond panels from two sheets made ofaluminium or aluminium alloys.

The publication “High Performance Airgap Heat Shields Using Blow-MoldedRoll-Bond Aluminum Technology” by V. J. Scott et al., published in theSAE Technical Paper Series (International Congress & Exposition,Detroit, Mich., Feb. 28–Mar. 3, 1994), describes a roll-bond panelproduction line which comprises straightening and brushing of the twostrips, application of the separation medium, preheating and rolling ofthe strips to form a composite strip, which is then subjected toannealing in a coil in a static furnace.

Therefore, this method is not a continuous method. The use of a staticfurnace enables more precise control of the annealing conditions thanmethods using a passage furnace, but the interruption represented by thestrip annealing results in economic drawbacks, reduces the productionline response time in relation to commercial demand and requiresintermediate product stock management.

A specific problem in the roll-bond method is the quality and durabilityof the channels formed. The European patent EP 0 703 427 (ShowaAluminium) proposes a method which aims to reduce the number of defectsduring expansion (rupture of channels or local absence of deformation).

According to the observations made by the applicant, existing productionlines do not enable the production of panels, particularly OSF panels,with strong mechanical properties. In addition, it is desirable toguarantee that the panels formed, before expansion, are free ofredhibitory defects.

The purpose of the invention is to provide a continuous roll-bond panelproduction method, which is suitable for the production of OSF panelswith strong mechanical properties and which enables, both for OSF andtwo-sided type panels, early detection of defective panels.

SUMMARY OF THE INVENTION

The invention relates to an aluminium OSF integrated circuit panelproduction method comprising surface preparation of two aluminium alloysheets, deposition on one of the sheets of a weld-proof ink in reservedareas corresponding to the design of the circuit, connection by rollingof the sheets together, and expansion of the channels corresponding tothe non-welded areas using a pressurised fluid, wherein one of thesheets is made of 1000 series alloy and the other of an alloy containingiron and manganese and such that Fe+Mn>0.8% (by weight), andpreferentially >1, or 1.5%. The iron and manganese alloy ispreferentially obtained by continuous casting of strips between twocooled rolls.

The invention also relates to a continuous aluminium alloy integratedcircuit panel production method comprising the following steps:

(a) supply of the production line with two aluminium alloy strips A andB,

(b) optionally, straightening of strips A and B,

(c) brushing of strips A and B,

(d) application on strip A of a weld-proof ink,

(e) optionally, quality control inspection of said application,

(f) preheating of strips A and B,

(g) application using a rolling mill of strip B on the surface of stripA to obtain a composite strip,

(h) annealing of the composite strip in a furnace,

(i) cooling of the composite strip,

(j) optionally, flattening of the composite strip,

(k) cutting of the composite strip into panels,

(l) optionally, a device enabling the elimination of panels comprisingweld-proof ink application defects, detected during the inspection instep e,

(m) transfer of the panels into an expansion press with several levels,

(n) expansion of the channel,

(o) removal of the panels from the press and stacking for packaging.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE represents, as a function of the annealingtemperature, the recrystallised fraction for 1050, 3003, 8040 and 8006alloy sheets produced by continuous casting.

DESCRIPTION OF THE INVENTION

The applicant noted that the alloys generally used to produce two-sidedroll-bond panels may be used, particularly those disclosed in the book“L'aluminium”, volume 1 “Production—Propriétés—Alliages—Fabrication desdemi-produits—Fabrications annexes”, mentioned above. To produce OSFpanels, it is necessary, as indicated in patent FR 13479949, during theexpansion of the channels, for one of the sides of the panels to bedeformed more easily than the other. Therefore, two different alloys areused for the two sides of the composite strip, a harder one forming theflat side, and another less hard one, which is deformed during expansionto form the channels of the circuit. For example, it is known to use thecombination of 1050 and 8040 alloys (according to Aluminum Associationreferences). However, the applicant noted during its tests that it ispreferable to use for the flat side a strip made of alloy containingiron and manganese and such that Fe+Mn>0.8% (by weight), andpreferentially >1, or 1.5%. An example of an alloy of this type of 8006alloy, wherein the composition registered at the Aluminum Association isas follows (% by weight):

Si<0.40 Fe: 1.2–2.0 Cu<0.30 Mn: 0.30–1.0 Mg<0.10 Zn<0.10.

The iron and manganese alloy strip is preferentially produced bycontinuous casting of strips, particularly by continuous casting betweentwo cooled rolls, for example using a Pechiney Aluminium EngineeringJumbo 3C™ machine. It is known that alloys containing manganese and/oriron obtained by continuous casting comprise, after a cold rollingprocedure performed directly after casting, i.e. with no homogenisationof the cast strip, a fine-grain microstructure giving a higherrecrystallisation resistance than the same alloys obtained from rollingingots. The microstructural properties of such strips obtained bycontinuous casting have been described in the literature, particularlyin the articles by M. Slámová´et al.: “Differences in StructureEvolution of Twin-Roll Cast AA8006 and AA8011 Alloys during Annealing”,published in the review Materials Science Forum, Vols. 331–337 (2000),pp. 829–834; “Impact of As-Cast Structures on Structure and Propertiesof Twin-Roll Cast AA8006 Alloy”, published in the review MaterialsScience Forum, Vols. 331–337 (2000), pp. 161–166; “Response of AA 8006and AA 8111 strip-cast cold rolled alloys to high temperatureannealing”, published in the Minutes of the ICAA6 Congress, Vol 2, pp.1287–1292: “Phase-Transformation Study of Two Aluminum Strip-CastAlloys”, published in the Minutes of the ICAA6 Congress, Vol 2, pp.897–902, but it has not yet been envisaged to use it to form an OSF typeroll-bond panel.

The invention also relates to an enhanced two-sided or OSF typealuminium alloy integrated circuit panel production method. In the restof the disclosure, the term “strip A” will be used to refer to thealuminium or aluminium alloy strip on which the weld-proof ink isapplied, “strip B” will be used to refer to the aluminium or aluminiumalloy strip which is applied to strip A, “composite strip” will be usedto refer to the strip formed from strips A and B, and “panels” will beused to refer to the panels formed by cutting the composite strip.

The continuous method according to the invention comprises the followingsteps:

(a) supply of the production line with strips A and B,

(b) straightening of strips A and B,

(c) optionally, brushing of strips A and B,

(d) application on strip A of a weld-proof ink,

(e) quality control inspection of said application,

(f) preheating of strips A and B,

(g) creation of a composite strip by passing strip A which comprises theink, and strip B, under a rolling mill,

(h) annealing of the composite strip in a furnace,

(i) cooling of the composite strip,

(j) optionally, flattening of the composite strip,

(k) cutting of the composite strip into panels,

(l) optionally, elimination of panels comprising separation mediumapplication defects, detected during the inspection e,

(m) transfer of the panels into an expansion press with several levels,

(n) expansion, preferentially simultaneously, of the panels on alllevels,

(o) removal of the panels from the press and stacking for packaging.

Strips A and B may be supplied by two coils. In a preferred embodimentof the invention, each of the two coils is equipped with a mobilejoining device, used to change each of the strips A and B withoutinterrupting the feed of the strips in the production line.

Before being introduced into the production line, it is advantageous todegrease the strips, for example using a flame method or any othermethod known to those skilled in the art.

It is advantageous to brush the surfaces of strips A and B intended tocome into contact. Rotary brushes equipped with steel bristles aresuitable for this purpose.

The weld-proof ink may be applied onto strip A using screen printingtechniques known to those skilled in the art. The quality controlinspection of said screen printing may be carried out by a qualifiedoperator. In a preferred embodiment of the invention, the quality ofthis application is preferentially inspected by an automatic industrialvision device capable of detecting redhibitory defects and of locatingthe position of defective circuits on strip A. This device acquires theprinted image and compares it to a reference considered to be perfect.In this way, this system makes it possible to eliminate, before theexpansion of the circuits, panels on which a redhibitory defect has beendetected.

Any continuous furnace known to those skilled in the art may be used asthe preheating furnace, for example a direct flame furnace. In apreferred embodiment of the invention, said furnace enables theregulation of the temperature so as to keep the temperature constantover the entire width of strips A and B in an interval between ±10° C.maximum, preferentially between ±7° C., or even more preferentially inan interval between ±5° C.

Strip B may be applied to strip A in a conventional rolling mill andpreferentially in a quarto rolling mill. In a preferential embodiment ofthe invention, the two rolls which come into contact with the strip arebrushed during rolling. The brushing device disclosed in the Frenchpatent FR 2568495 is suitable for this purpose.

Any continuous furnace known to those skilled in the art may be used forthe annealing of the composite strip. In a preferred embodiment of theinvention, said furnace enables the regulation of the temperature so asto keep the temperature constant over the entire width of the strip inan interval between ±10° C., preferentially between ±7° C., or even morepreferentially in an interval between ±5° C. The composite strip may becooled by spraying with any liquid or gas coolant, and preferentially bysprinkling with water.

If it is necessary to flatten the composite strip at this stage, saidflattening may be carried out for example mechanically by means ofvarying insertion of the strip between two metal roller sheets.

The composite strip may be cut into panels using fixed shears. In thiscase, it is necessary to add a strip accumulator which makes it possibleto cut without interrupting the continuous feed of the strip. In apreferred embodiment of the invention flying shears are used, renderingthe strip accumulator liable to induce defects on the composite stripsuperfluous.

In a preferred embodiment of the invention, the panels wherein defectivecircuits have been detected during the inspection are then eliminated,before the panels of acceptable quality are transferred to the expansionpress. This transfer is advantageously carried out by loading the panelsinto a lift. Then, the panels are transferred using a robot, for examplewith a six-axis robot, into the press.

The expansion press comprises several levels, preferentially at leastfour levels, and even more preferentially at least eight levels. In saidpress, the circuits are expanded using a pressurised fluid via a needlewhich is inserted into the expansion channel, between the two sides ofeach panel. The panels in the press may be expanded one after the otheror, preferentially, simultaneously. In a preferential embodiment of theinvention, said press is of a design such that it enables the expansionof OSF panels, i.e. panels comprising expanded circuits on one sideonly, the other side being flat, and two-sided panels, i.e. panelscomprising expanded circuits on both sides. To produce OSF panels, aback pressure is applied to the side opposite the flat side, usingtechniques known to those skilled in the art and described, for example,in the patent FR 2561368 mentioned above.

The panels are advantageously removed from the press by a robot, forexample a six-axis robot, which unloads the expanded panels from thepress to a chute, which transfers the panels to a stacker used to formstacks of panels ready to be packaged for shipment.

In a preferred alternative embodiment of the invention, strips A and Band the composite strip are centred. For example, centring is usefulbefore the strip enters the roll nip of the rolling mill. FIG. 1 shows apreferred embodiment of the invention.

The invention as described above may be advantageously applied to theproduction of any roll-bond panels for existing refrigerating appliancesor for other heat exchange or transfer applications.

It may also be implemented for the production of panels for structuralapplications, such as reinforcements for automobile bodywork. Theapplicant has noted that, in certain cases, it may be advantageous touse a composite panel produced from more than two type A strips, whichmay contain a single circuit or several circuits, identical or not. Inthis case, the term “type A strip” refers to the aluminium or aluminiumalloy strip(s) on which the weld-proof ink is applied. The term “type Bstrip” refers to the aluminium or aluminium alloy strip(s) which will beapplied onto the type A strip(s), which do not comprise any screenprinting. For example, a roll-bond panel composed of three superimposedstrips comprising two superimposed circuits is composed of two type Astrips and one type B strip. The term “composite strip” refers to thestrip formed from type A and type B strips and the term “panels” refersto the panels formed by cutting the composite strip.

In this case, the continuous method according to the invention comprisesthe following steps:

(a) supply of the production line with two type A strips and one type Bstrip,

(b) straightening of the type A and type B strips,

(c) brushing of the type A and type B strips,

(d) application of a separation medium onto the type A strips,

(e) optionally, quality control inspection of said application,

(f) preheating of the type A and type B strips,

(g) creation of a composite strip by passing the type A strips whichcomprise the separation medium, and the type B strip, under a rollingmill,

(h) annealing of the composite strip in a furnace,

(i) cooling of the composite strip,

(j) optionally, flattening of the composite strip,

(k) cutting of the composite strip into panels,

(l) optionally, elimination of panels comprising ink applicationdefects, detected during the inspection (e),

(m) transfer of the panels into an expansion press with several levels,

(n) expansion, preferentially simultaneously, of the panels on alllevels,

(o) removal of the panels from the press and stacking for packaging.

EXAMPLE 1

The line is supplied by a mobile joining device used to change each ofthe strips A and B without interrupting the feed of the strips in theproduction line. This carriage is equipped with mobile welding machineswith no metal filler to join the strips from the two metal coils.

Strips A and B are straightened by a motorised roller straighteningmachine.

The surfaces of strips A and B intended to come into contact are brushedby motorised metal brushes.

The screen printing is carried out in a pressurised closed chamber,making it possible to minimise dust deposition and the appearance ofdefects on the strip. Screens wherein the web structure and threaddensity are adjusted according to the desired print are used; the screenprinting is performed using techniques known to those skilled in theart. The adhesive-proof ink is supplied to the web automatically,enabling good homogeneity of the quantity of ink. The screens arechanged when the series is changed without shutting down the line, in asemi-automated fashion. After screen printing, an additional spot of inkis added to strip A at the end of the patterns; said spot is used as amark when the composite strip is cut into panels.

The quality of the screen printing is inspected by an industrial visiondevice, equipped with linear cameras. All the patterns are acquired,processed and compared to a reference image. Said device is used toverify the functional dimensions of the patterns and to locate anydefects (such as superfluous spots, insufficient ink or impreciselydefined edges). The position of the defective patterns is located by themonitoring computer to be able to remove the panels comprising saiddefective patterns before the expansion step.

The preheating furnace is a passage gas furnace. It is composed of twoparts used to heat strip B and strip A successively. Its output is 1800kW. The temperature of the strip in the furnace is typically of theorder of 400° C., but may reach 500° C., depending on the alloys used.The furnace comprises two by three heating zones. The temperature iskept constant by a regulation system at ±7° C.

The rolling mill used is a quarto rolling mill making it possible toobtain rolling forces of the order of 1400 tonnes, with the possibilityof variable balancing.

The annealing furnace is a 1220 kW output passage gas furnace. Thetemperature of the composite strip in the furnace is typically of theorder of 400° C. but may reach 500° C., depending on the alloys used.The furnace comprises four heating zones. The temperature is keptconstant by a regulation system at ±7° C.

The composite strip is flattened by a flattening machine comprising 17variable interlacing rollers, known to those skilled in the art.

An ultrasound sensor is used to detect the spot of ink deposited duringthe screen printing step and activates the cutting of the compositestrip into panels by flying shears. The panels are fed into a lift andare loaded in batches of eight into the expansion pressure using asix-axis robot.

The expansion press is a 2500 tons hydraulic press enabling thesimultaneous expansion of the panels on all the levels. Programmedcycles enable the on-line expansion of two-sided and OSF panels. For OSFpanels, a back pressure is applied on all the levels in addition to theexpansion pressure. The expansion cycles are controlled by a computer.The press is equipped with leak detection devices during expansion andenables the elimination of the defective panels detected.

Panels with expanded channels are unloaded from the press by a secondsix-axis robot onto a chute. The method's parameters are adjustedaccording to the feed speed measured at several points of the line. Thespeed of strips A and B may reach 15 m/min. The speed of the compositestrip may reach 30 m/min, for a rolling ratio of 2. The different linesettings are controlled automatically from a product database. The widthof the strips used may reach 700 mm.

EXAMPLE 2

OSF roll-bond panels were produced by following the method in example 1.Strip A is made of 8006 alloy of the following composition (% byweight):

Si=0.28, Fe=1.20, Cu=0.024, Mn=0.37, Mg=0.0013, Ti=0.017,

and was produced by continuous casting between rolls, with nohomogenisation of the cast strip before rolling. The cast thickness was7 mm, and the cast strip was cold-rolled up to 1.2 mm, and thensubjected to restoration annealing for 2 hours at 220° C.

Strip B is made of 1050 alloy, 1.26 mm thick, obtained by hot-rollingfollowed by cold-rolling of rolling ingots.

When removed from the preheating furnace, the temperature of strip A was480° C., and that of strip B was 380° C. The rolling ratio applied was2. The composite strip was then annealed in the annealing furnace atdifferent temperatures mentioned in table 1. The Vickers hardness of thetwo sides after annealing is also given in table 1.

TABLE 1 Vickers Vickers hardness of hardness of Annealing panel on panelon temperature “strip A” “strip A” Reference [° C.] side side 1 380 48.924.5 2 400 46.8 23.8 3 420 45.5 23.3 4 430 43.5 25.2 5 440 42.5 23.0 6460 40.2 24.7

According to the observations made by the applicant, an annealingtemperature of 400° C. represents the best compromise between therequirement relating to the flatness and the surface appearance of theflat side (favoured by high hardness of the strip A side) and therequirement for sufficient form of the panel to enable the expansion ofthe channel without rupture (favoured by low hardness of the strip Bside). In any case, it is preferable for the hardness of the panel onthe strip A side to be greater than 40 Vickers and preferentiallygreater than 43 Vickers or even 45 Vickers.

EXAMPLE 3

OSF roll-bond panels were produced by following the method in example 1.Strip A is made of 8040 alloy produced from rolling ingots. Thethickness of strip A is 1.26 mm and it was subjected to restorationannealing for 10 hours at 250° C.

Strip B is made of 1050 alloy, 1.26 mm thick, obtained by hot-rollingfollowed by cold-rolling of rolling ingots.

When removed from the preheating furnace, the temperature of strip A was480° C., and that of strip B was 380° C. The rolling ratio applied was2. The composite strip was then annealed in the annealing furnace attemperatures of 400 and 440° C., respectively. The hardnesses of the twosides after annealing are given in table 2.

TABLE 2 Vickers Vickers hardness of hardness of Annealing panel on panelon temperature “strip A” “strip A” Reference [° C.] side side 1 400 38.025.1 2 440 36.2 25.2

It is noted that lower hardnesses are obtained on the strip A side thanin example 2 for equivalent conditions. It cannot be envisaged to reducethe annealing temperature significantly to increase the hardness of thecomposite strip on the strip A side, since the recrystallisation of the1050 alloy, which gives it its suitable form in the expansion press,requires, under the conditions of the method according to example 1, atemperature of at least 370 to 380° C.

EXAMPLE 4

A laboratory test was conducted to verify that the 8006 alloy stripsobtained by continuous casting show a higher recrystallisationresistance than the other strips generally used to produce OSF roll-bondpanels. It is known that the hardness of recrystallised strips is lowerthan that of non-recrystallised strips; given that a sufficient hardnessis needed to be able to use a strip as a flat side of an OSF roll-bondpanel, this test makes it possible to preselect the strip that can beused for this purpose.

8040, 8006, 3003 and 1050 strips and sheets, capable of being used toproduce roll-bond panels, were prepared by cold rolling. The 8006 alloywas prepared by continuous casting with no homogenisation. The reductionduring the cold rolling was by a factor of 2. The sheets were thenannealed in salt bath furnaces for 15 s at variable temperatures between380 and 440° C. and the recrystallised fraction was then determinedusing a metallographic observation technique known to those skilled inthe art.

It is noted in the diagram in the figure that 1050 alloy sheetsrecrystallise significantly at relatively low temperatures (<400° C.),while 8006 alloy sheets do not recrystallise at all over the entiretemperature range studied, which is particularly suitable for use in themethod according to example 1.

1. Method for producing an aluminum alloy one side flat integratedcircuit panel including a flat side and a deformed side, comprising thesteps of: surface preparation of two aluminum alloy sheets, a first ofsaid sheets corresponding to the deformed side, and a second of saidsheets corresponding to the flat side, depositing on one of the sheets aweld-proof ink in reserved areas corresponding to a circuit design,welding the sheets by rolling the sheets together, the reserved areasforming non-welded areas, and expanding channels corresponding to thenon-welded areas using a pressurized fluid, wherein the deformed side ismade of a 1000 series alloy and the flat side is made of an alloycontaining iron and manganese, such that Fe+Mn>0.8% (by weight). 2.Method according to claim 1, wherein Fe+Mn>1%.
 3. Method according toclaim 2, wherein Fe+Mn>1.5%.
 4. Method according to claim 1, wherein theflat side is formed of an 8006 alloy.
 5. Method according to claim 1,wherein the flat side sheet is obtained by continuous strip casting. 6.Continuous method for producing an aluminum alloy integrated circuitpanel, comprising the steps of: (a) supplying a production line with analuminum alloy strip A and an aluminum alloy strip B, (b) optionallystraightening strips A and B, (c) brushing strips A and B, (d) applyinga weld-proof ink to strip A in reserved areas corresponding to a circuitdesign, (e) optionally, conducting a quality control inspection of saidapplication, (f) preheating strips A and B, (g) joining, using a rollingmill, strip B on a surface of strip A to obtain a composite strip, thereserved areas forming non-welded areas, (h) annealing the compositestrip in a furnace, (i) cooling the composite strip, (j) optionally,flattening the composite strip, (k) cutting the composite strip intopanels, (l) optionally, eliminating panels comprising defective inkapplication, detected during the optional quality control inspection,(m) transferring the panels into an expansion press with a plurality oflevels, (n) expanding channels in the composite strip corresponding tonon-welded areas, and (o) removing the panels from the press andstacking for packaging.
 7. Method according to claim 6, wherein strips Aand B are joined together without interrupting the supplying of strip Aand strip B.
 8. Method according to claim 6, wherein said annealing ofthe composite strip is carried out such that the composite strip is keptover its entire width at a temperature in an interval between ±10° C. 9.Method according to claim 8, wherein the temperature interval is ±5° C.10. Method according to claim 6, wherein the preheating of strips A andB is carried out such that each of said strips is kept over its entirewidth at a temperature in an interval between ±10° C.
 11. Methodaccording to claim 10, wherein the temperature interval is ±5° C. 12.Method according to claim 6, wherein the expansion press is equippedwith at least 4 levels.
 13. Method according to claim 12, wherein theexpansion press is equipped with at least 8 levels.
 14. Method accordingto claim 6, wherein the cutting of the composite strip is carried outusing flying shears.
 15. Method according to claim 6, wherein therolling mill is a quarto rolling mill.
 16. Method according to claim 6,wherein the composite strip at the rolling mill outlet travels at aspeed greater than 20 meters per minute.
 17. Method for continuousproduction of aluminum alloy integrated circuit panels formed from atleast three metal strips, comprising the steps of: (a) supplying aproduction line with two strips of a type A and one strip of a type B,said strips of type A being more easily deformable than said strip oftype B, (b) straightening the type A and type B strips, (c) brushing thetype A and type B strips, (d) applying of a weld-proof ink onto the typeA strips in reserved areas corresponding to a circuit design, (e)optionally, conducting a quality control inspection of said application,(f) preheating the type A and type B strips, (g) forming a compositestrip by passing the type A strips and the type B strip through arolling mill, the reserved areas forming non-welded areas, (h) annealingthe composite strip in a furnace, (i) cooling the composite strip, (j)optionally, flattening the composite strip, (k) cutting the compositestrip into panels, (l) optionally, eliminating of panels comprisingdefective ink application detected during the optional inspection, (m)transferring the panels into an expansion press with a plurality oflevels, (n) expanding channels in the composite strip corresponding tonon-welded areas on all levels, by deforming said strips of type A, (o)removing the panels from the press and stacking for packaging. 18.Method according to claim 17, wherein the expanding of the channels issimultaneous on all levels.